Dimeric Capsules by the Self‐Assembly of Triureidocalix[6]arenes through Hydrogen Bonds

Abstract

A number of calix[6]arenes bearing ureas at the upper rim positions of alternate rings 1, 3 and 5 were prepared and studied in detail by NMR spectroscopy and gel permeation chromatography. N-Unsubstituted ureas were shown to dimerize through a cyclic array of hydrogen bonds to give cylindrical cavities capable of encapsulating small molecules such as dichloromethane, benzene and fluorobenzene. Slow equilibria between dimer and monomer were observed in [D6]DMSO-CDCl3 mixtures. By contrast, N-substituted ureas are monomeric. All urea monomers with bulky O-substituents display a solvent-dependent, slow equilibrium between C3v and Cs cone conformations.

Redox‐Switchable Calix[6]arene‐Based Isomeric Rotaxanes

“…Mass spectra were determined in ESI mode. Compounds 1 a , 1 b , 2 a , 7 a , 13 , 5 , 10 , 14 , R‐C6C6 , axle DOV , and wheel Cx were synthesized according to reported procedures.…”

Nichtkovalente Synthese mit Wasserstoffbrücken

“…[241] Calix [4]arene gehören zur gleichen Verbindungsklasse wie Resorcarene und Cavitanden. [249,250] Die resultierenden Kapseln haben kleine Hohlräume, die Gäste wie N-Methyl-4-picoliniumiodid bzw. [245] Lediglich Calix [4] [6]arene dimerisieren, wenn sie mit drei Carbonsäure-oder drei Harnstoffeinheiten substituiert sind.…”

Theoretical study of the geometrical and electronic structures and thermochemistry of spherophanes

“…The building blocks that are widely used for the preparation of molecular cages include (among others): calixarenes [9,10], resorcinarenes [11,12], glycorils [13,14], and spherands [15]. In order to facilitate the formation of the cage and avoid side compounds, preorganisation of the subunits is necessary and the use of template compounds is usually recommended [13,14,16,17].…”